Fuel-effusion prevention valve

Abstract

A fuel-effusion prevention valve includes a first housing member having an evaporation passage, a first engaging portion and a first cylindrical portion, and a second housing member having a partition portion, a communicating passage, a second engaging portion and a second cylindrical portion. The first cylindrical portion is formed so as to extend axially from the first engaging portion, and its diameter is smaller than that of the second engaging portion. The second cylindrical portion is formed so as to extend axially from the second engaging portion. A floating valve is disposed in a chamber so as to be able to open and close the valve hole in response to its buoyancy due to fuel flowing into the second chamber through the communicating passage. The first cylindrical portion is fused with the second cylindrical portion. A circular seal member is fitted into an installation hole formed on the fuel tank and its inner hole is fitted onto the outer circumferential surface of the first cylindrical portion.

What is claimed is: 
     
       1. A fuel-effusion prevention valve, comprising: a resinous cylindrical housing having first and second engaging portions each formed on an outer circumferential portion of said housing, a partition portion which axially defines first and second chambers in an interior of said housing, a valve hole formed on the partition portion so as to communicatively connect the first and second chambers, an evaporation passage which communicatively connects the first chamber with a filter and a communicating passage which communicatively connects the second chamber with an interior of a fuel tank,   a floating valve disposed in the second chamber as to open and close the valve hole in response to buoyancy due to fuel flowing into the second chamber through the communicating passage and,   a circular seal member fitted into an installation hole formed on the fuel tank, the seal member having an inner hole defined on the outer circumferential surface of the housing between the first and second engaging portions, wherein   the housing further includes a first housing member having the evaporation passage, the first engaging portion and a first cylindrical portion formed so as to extend axially from the first engaging portion and with a diameter smaller than that of the second engaging portion,   a second housing member having the partition portion, the communicating passage, the second engaging portion and a second cylindrical portion formed so as to extend axially from the second engaging portion, the outer circumferential portion of the second cylindrical portion and the inner circumferential portion of the first cylindrical portion being fused to each other.   
     
     
       2. A fuel-effusion prevention valve as claimed in claim 1, wherein a stepping portion with a diameter larger than that of the second cylindrical portion and smaller than that of the second engaging portion is formed on the second cylindrical portion and a circular groove in which the stepping portion is received is formed on an end of the first cylindrical portion. 
     
     
       3. A fuel-effusion prevention valve as claimed in claim 1, wherein a communicating hole communicatively connects the first and second chambers and that is in parallel with the valve hole is formed on the partition portion, and a relief valve that normally closes the communicating hole and opens the communicating hole when the pressure in the second chamber becomes higher than a predetermined value is disposed in the first chamber. 
     
     
       4. A fuel-effusion prevention valve as claimed in claim 1, wherein the floating valve includes a disk portion, a valve portion formed on a center of a first side of the disk portion and that opens and closes the valve hole, a columnar portion that extends from a second side of the disk portion in the axial direction, and a plurality of rib portions radially formed on an outer circumference of the columnar portion.